Parabens


These methyl, ethyl, propyl, and butyl esters of hydroxybenzoic acid have bacteriostatic and fungicide properties and are the most widely used preservatives in food, cosmetics and medications (more than 300 pharmaceutical categories).
 
Incidence
0.8% of chronic dermatitis (skin tests).
 
3% of delayed cutaneous manifestations.
 
0.9% of drug allergies.
 
Risk factors
Damaged skin (leg ulcer, stasis dermatitis).
 
Previous sensitization by substances with a para-amine function.
 
Localization on the face or the neck.
 
Clinical manifestations
After topical use: Contact eczema.
 
After oral use: Eczema-like eruptions, pruritus, urticaria. Insidious chronic dermatitis is frequent especially if corticosteroids are associated.
 
After systemic administration:
  • Cutaneous: erythema, urticaria, pruritus, angioedema.
     
  • Respiratory: dyspnea, bronchospasm, worsening of ongoing asthma.
Diagnostic methods
Cutaneous testing.
  • Patch-tests are often positive in patients with contact dermatitis. Parabens mix belongs to the European patch-tests standard series and contains 3% of methyl, ethyl, propyl and butyl para-hydroxybenzoates.
     
  • Intradermal skin-tests should be performed with a 5% concentration of methylparaben, ethylparaben, propylparaben, and butylparaben in order to avoid false negatives. A few positive results have been reported in patients with immediate reactions.
Mechanisms
IgE-mediated hypersensitivity is suggested by the following findings: positive Prausnitz-Küstner tests reported in several cases, immediately positive intradermal skin tests. However, IgE antibodies have never been detected.
 
Cell-mediated hypersensitivity is responsible for contact dermatitis.
 
Cross-sensitivity may occur between parabens and molecules possessing a free amine group in the para position (benzocaine, para-phenylendiamine and sulfonamides). The only difference between such products and parabens is the presence of a hydroxy instead of an amine group in the para position. Cross reactivity between p. amine and p. hydroxyl compounds has been documented.
 
Management
Avoidance is difficult.

References

  1. Verhaeghe I, Dooms-Goossens A, "Multiple sources of allergic contact dermatitis from parabens", Contact. Dermatitis, 1997; 36 (5): 269-70
  2. Rycroft R.J.G, Menne T, Frosch P.J, "Textbook of contact dermatitis", 2nd Ed.Springer-Verlag Berlin, 1995; 437-8 
  3. Fisher A.A, "The parabens: paradoxical preservatives" Cutis, 1993; 51 (6): 405-6 
  4. Chichmanian R.M, Mignot G, Spreux A, Cassuto D, Manassero J, "Manifestations allergiques multiples. Rôle d’un excipient", Thérapie, 1985; 40: 365-7. 
  5. Nagel J.E, Fuscaldo J.T, Fireman P, "Paraben allergy", JAMA, 1977; 237: 1594-5.

As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.